26 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
broken into by some burrowing animal and many colonies were aban- 
doned. This cycle of change must several times have worked over the 
surface materials of the campos of Brazil and facilitated the work of 
erosion by winds and rain. 
When it is recalled that a large insectivorous fauna including the 
anteaters, Myrmecophagidae (Vermilinguia), inhabit the ant-occupied 
surface of Brazil and that this group is specialized with reference to 
the ants and that traces of this organic adaptation go back to Pliocene 
times, it is evident that ants and anteaters have exercised an important 
function in the geologic processes which have worked together in the 
evolution of the surface deposits of Brazil. Fossil ants are numerous 
in the Oligocene beds of Florissant in Colorado (Scudder) and ant- 
eaters appear in the Miocene Santa Cruz formation of South America, 
dates which are as far back if not earlier than the beginnings of the 
present surface deposits of the Brazilian highlands. 
August 29th.— The road northward from the camp at the dike 
passed over alternating beds of red shale and yellowish to reddish 
sandstones, dipping gently to the northwest towards the southern 
margin of the trap sheets, whose escarpment, as far as it could be seen, 
extended in a northeast-southwest direction roughly parallel to the 
strike of the underlying sediments. From the top of one of the 
monoclinal ridges between the Rio Ponte alto and the Rio Canoas, this 
escarpment could be traced to the eastern horizon where a conical 
outlier stood out in clear relief as a monument to the erosion of the 
trap cover which formerly extended over the Lages area. 
Fic. 4.— Field sketch of the trap plateau northwest from Rio Marombas in 
Santa Catharina. 
The monoclinal structure of the sediments results in a series of ridges 
with steeper faces on the southeast and longer gentle slopes to the 
northwest. At about twelve kilometers from camp we crossed the 
Canoas River, and continued northward to the north bank of the Rio 
Ponte alto where we camped by a covered bridge. The stream at this 
point flows in a channel about twenty feet deep over sandstones with 
an active drainage. . 
August 80th.— After a march of an hour and fifty minutes from 
camp we passed over sandstones striking northwest and dipping about 
15 degrees to the northeast. About forty-five minutes later we 
